The present invention relates to a heat processing apparatus such as a heating apparatus and a preheating apparatus to be installed in a semiconductor manufacturing system for manufacturing a semiconductor device.
In a photolithography process for manufacturing a semiconductor device and an LCD, resist is coated on a substrate, and the resultant resist coating film is exposed to light and developed. Such a series of processing is carried out in a coating/developing system. The coating/developing system has heating units such as a prebake unit and a postbake unit. These heating units have a hot plate with a built-in heater of a resistance heating type.
The wafers W are processed in units (lots) each consisting of, e.g., 25 wafers. Each lot is processed under the same recipe (individual processing program). Heating is performed under the conditions such as prebaking temperature and postbaking temperature according to the recipe. The wafers belonging in the same lot are heated under the same conditions.
Then, when one lot is completed and a new lot is subjected to the processing, the recipe is switched to a new recipe, accordingly, so that temperature of the hot plate changes. When the heat processing temperature is allowed to change from a low temperature range to a high temperature range, the temperature of the hot plate can be changed immediately if electric supply to the hot plate is increased. However, the heat processing temperature is allowed to switch from the high temperature range to the low temperature range, the temperature of the hot plate cannot be decreased in a short time. This is because a conventionally used heating unit employs an air cooling method. To be more specifically, the hot plate is cooled by blowing a cold air thereon. Since the hot plate (metal disk of approximately 16 mm thick) has a large heat capacity, it takes a long time to decrease the temperature of the hot plate to a desired temperature, thus lowering a throughput.
To overcome the low throughput, if hot plates are provided so as to correspond to the number of different recipes, the hot plates will occupy a huge space. As a result, the apparatus will increase in size and its control system will be more complicated.
To use a single hot plate for different heat processes, it is possible to consider an apparatus equipped with a hot plate having a refrigerant circulating therein to cool the hot plate in a short time. The apparatus of this type has a problem in that the structure of the hot plate becomes complicated, increasing the manufacturing cost.